This invention relates to a method of making knitting tools from a stamped blank. Further, the invention relates to a stamped knitting tool for textile machines and is of the type having rounded, chamfered or fractured edges. By "knitting tool" there are meant, for example, latch needles, springbeard needles, compound needles, latchless needles (such as plush hooks for making plush wear) as well as sinkers.
Knitting tools of the above-outlined type have to be manufactured in most cases in large quantities and have to be of uniform, good quality. Such requirement pertains particularly to those edges of the knitting tools which contact the thread to be knitted or which are in contact with walls of guide channels or needle channels and move relatively thereto.
German Patent No. 2,637,078, to which corresponds U.S. Pat. No. 4,151,783, discloses a method and an apparatus for machining the butt of stamped knitting machine needles. Starting from a stamped component, the stamped butt edges are machined by cutting in a milling process for obtaining the desired butt shape. The needle butt may be rounded or chamfered at its upper or lower edges contacting the cam of the knitting machine.
German Patent No. 2,911,195, to which corresponds U.S. Pat. No. 4,417,454, also relates to the shaping of the needle butt. According to this reference, the needle butt is provided in an embossing step with groove-like depressions which extend over the entire length of the needle butt on the flat sides thereof. An embossing tool provided for this purpose receives the butt of a needle stamped from a steel ribbon (stock material) and, as the tool is closed, it presses the above-noted grooves into the flat sides of the needle butt. The fractured surfaces appearing upon the stamping of the needle butt are in this manner squeezed outwardly and changed into a predetermined shape. The remainder of the needle is not affected by the embossing process.
German Patent No. 4,442,943, to which corresponds U.S. Pat. No. 5,582,038, describes a stamped knitting tool which has a butt provided with plastic-filled apertures. In the essentially strip-shaped blade longitudinal, slot-like openings are provided whose peripheral edges on both sides of the openings are pinched to permit a form-locking securement of the plastic filling. During such a pinching operation the peripheral edges are, from both sides of the flat, strip-like blade, pressed towards one another, whereby the material flowing towards one another deforms the wall of the slit-shaped opening. Between the thus-chamfered edges of the opening the slot wall is of concave configuration.
According to German Offenlegungsschrift 34 01 874, in the manufacture of welt hooks, embossing and stamping steps are combined for shaping the needle blade. According to this method, particularly the depressions to be provided in the needle blade are, before stamping of the needle blade, embossed into the metal ribbon, involving the displacement of material. The stamping step which determines the dimensions of the needle is thus performed subsequently to maintain the needle at the desired coarse (preliminary) outer contour. Fractured edges are subsequently eliminated or taken into consideration.